There's “always the possibility that it's a foreshock," Robert Graves of the U.S. Geological Survey told the Los Angeles Times.

"We’re continuing to analyze the data, but at this point, this seems to be what I would call a rather typical earthquake," he said of the L.A. tremor.

According to USGS, foreshocks are "relatively smaller earthquakes that precede the largest earthquake in a series which is termed the mainshock. Not all mainshocks have foreshocks," the Monitor reported.

There's no way to predict them, the Monitor noted.

Earthquakes, though frequent in California, usually happen far from places were people live, Erin Burkett, a geophysicist with the USGS Science Application for Risk Reduction Project, told the Monitor.

Quakes are caused by the glacially slow adjustments made in the alignment around the Pacific Plate, the world's largest tectonic plate, as it slides northwest past the American plate, the Monitor noted.